An erection you consciously attempt to achieve in order to be polite and/or appreciative to a woman. Typically in response to an unattractive naked woman, or an inartfully executed handjob, it is an attempt to spare her the insult of a flaccid penis.

The girl in the hot tub was prettyfat, but since she'd taken her top off I tried to work up a courtesy boner, you know, to be chivalrous.